Structure of Blood Vessels- 1 Flashcards
Left Ventricle
Function:
Mean pressure:
Structural features:
Function: pump
Mean pressure: 95 mmHg
Structural features thick muscular walls, inlet & outlet valves
Large arteries
Function:
Structural features:
Function: Conducting, dampen flow
Structural features: elastic fibres
Medium-sized arteries
Function:
Mean pressure:
Structural features
Function: distributing, push blood to areas of demand
Mean pressure: 95-85 mmHg
Structural features: muscular walls to control diameter + CT for strength
Arterioles, metarterioles, precapillary sphincters
Function:
Mean pressure:
Structural features
Function: control pressure flow
Mean pressure: 85-35
Structural features: smooth muscle to control diameter, little CT
Capillaries
Function:
Mean pressure:
Structural features:
Function: slowed flow for gas/nutrient exchange
Mean pressure: 35-15
Structural features: endothelium, no muscle or CT
Venules
Function:
Mean pressure:
Structural features:
Function: collecting vessels (small veins)
Mean pressure: 15-0
Structural features: thin walled, large diameter
Veins
Mean Pressure:
Structural Features:
Mean Pressure: Low
Structural Features: Thin walled, variable structure, valves to assist return
Right Atrium
Mean Pressure:
Structural Features:
Mean Pressure: 0-2
Structural Features: Thin, muscular walls
The collecting system makes up __% of Blood volume
70%
Elastic arteries
The aorta and pulmonary arteries, which occur jsut downstream of the ventricles.
They fuction to store blood during ‘Ventricular ejection’ or systole, then recoil during ventricular filling (diastle), to ensure steady blood flow from the heart.
Elastic Arteries:
Tunica Adventitia
Usual collagen(restraint) and elastic fibres, small blood vessels “vasavasorum” and autonomic nerves
Elastic Arteries:
Tunica Media
Well defined. Many lamellar units (50-60 in aorta). Each unit is made up of an elastic lamina, smooth muscle and collagen fibres. These run mainly in a circular orientation around the vessel
**smooth muscle has little effect due to large lumen
Elastic Arteries:
Tunica Intima
Well defined. Thicker than in muscular arteries (up to 20% vessel wall), and contains longitudinal elastin fibres in the subendothelial CT. Run in a circular orientation around the vessel
IEL present but indistinguidable
IEL and EEL of elastic arteries
Internal Elastic lamina: present but indistinguishable from elastic laminae of media (in TI)
External Elastic laminae: between media and adventitia
Muscular Arteries: Tunica Intima
1) Endothelium
2) BM of endothelium
3) Subendothelium CT
4) A thick distinctive IEL. Smooth in life but with longitudinal folds after death
Muscular Arteries: Tunica Media
Middle and thickest coat.
Smooth muscle fibres control vessel diameter.
Elastic fibres gives resiliency.
Collagen fibres limit expansion to prevent rupture.
**outer margin sometimes includes a EEL, never as prominent as the IEL
Muscular Arteries: Tunica Adventitia
Outermost coat. Usually only collagen and elastin fibres. Vasa vasorum to service the outer layers of the vessel wall (these usually only present in larger muscular arteries)
Arterial Disease: Atherosclerosis
Narrowing of arteries by plaque filling. Influenced by lifestyle
Arterial Disease: Berry Anuerysm
Often found in the brain, upon rupture can lead to a stroke.
Bleeding into the media wall can result
Arterial Disease: Dissecting Aneurysm
AAA: Abdominal Aortic Aneurysm
No way to predict
Weakness in wall, usually congenital, can lead to bleeding in the vessel wall
High risk, high % mortality
Arterial Disease: Hypertension
Thickening of the vessel wall > high blood pressure
Normal BP: 120/80
Hypertension: >140/90
We see a narrowed lumen, duplication of IEL, thickening of the media (so SM increases) and thickening of the adventitia.
Very thick wall to lumen ratio.
Arterioles
Smallest of the muscular arteris
- overall diameter of 100micrometers or less
- 3 or less SM layers in media
- Wall thickness = lumen
Arterioles: Tunica Intima
endothelial cells overlying a basal lamina. IEL only present in larger arterioles
Arterioles: Tunica Media
Thicker muscle coat in the media relative to the lumen then any other vessel. Therefore it is at the arterioles that the biggest pressure drop occurs, as variation in diameter has a huge effect on blood pressure.
